Increasing the RIP Input Queue

Problem

You want to increase the size of the RIP input queue to prevent your low-speed router from losing routing information.

Solution

To increase the size of the shared RIP queue, use the input-queue configuration command:

Router2#configure terminal 
Enter configuration commands, one per line. End with CNTL/Z.
Router2(config)#router rip
Router2(config-router)#input-queue 200
Router2(config-router)#end
Router2#

Discussion

This command allows you to control how much incoming RIP update information the router can hold before it has can process the information and integrate it into its routing table. Sometimes a router simply can't keep up with all of the information that it receives. This is most likely to be the case with less powerful routers on a busy network with many routes.

Bear in mind that each RIP update packet can hold up to 25 routes, and the default queue size is more than adequate to hold this many routes. So the input-queue size is only likely to be a problem if you have many times this number of routes, or if you have many routers all sharing the same segment. If this is the case, and you find that a less powerful router is randomly losing routes from its table, then it is relatively safe and easy to increase this queue depth.

The default value is 50. In this recipe, we have increased the queue depth to 200. This is a good starting point if you think that you have a queue depth problem. You can set this value to anything from 0 to 1024, although it is not clear why you would want to decrease the queue depth.

Recipe 6.10 shows another, alternative solution to this same problem. Instead of increasing the queue size on the slower router, you may opt to change the interpacket delay on the faster routers. And, in some cases, it may be necessary to combine both of these solutions.